Re: [PATCH container] api: template: allow creating template from ct with disk on LVM

["Elias Huhsovitz" <e.huhsovitz@proxmox.com>]

I agree with @Fiona [1], but IMO this a good intermediate solution and I
don't see any downside in applying this.

The current state is somewhat annoying and this patch makes the
behaviour more consistent with VM equivalent function.

I gave this a quick test with a container containing 2 volumes:
- Root Disk: lvm-thin
- mp0: lvm

Creating the template worked without issues. 

When attempting to create a linked clone of the template, the user is
correctly stopped with an error.

Creating a full clone worked without any issues.

Reviewed-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>
Tested-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>

[1] https://lore.proxmox.com/pve-devel/328e1266-003a-42fd-bfea-2801b5afb88d@proxmox.com/

On Thu Mar 12, 2026 at 7:27 PM CET, Lukas Sichert wrote:
> Currently, in the UI, one can create a template from a VM with a disk on
> LVM storage, but not from a container. This is because the LVM plugin
> does not have the functionality to create base images from disks
> implemented. While the system simply skips this function for VMs, it
> throws an error and aborts for LXC containers.
>
> To allow converting to a template, skip the volumes where the required
> functionality is not present by exiting early instead of aborting.
>
> Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
> ---
>  src/PVE/LXC.pm | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index caba952..e77d208 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -1613,17 +1613,7 @@ sub template_create {
>  
>              my $volid = $mountpoint->{volume};
>  
> -            die "Template feature is not available for '$volid'\n"
> -                if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
> -        },
> -    );
> -
> -    PVE::LXC::Config->foreach_volume(
> -        $conf,
> -        sub {
> -            my ($ms, $mountpoint) = @_;
> -
> -            my $volid = $mountpoint->{volume};
> +            return if !PVE::Storage::volume_has_feature($storecfg, 'template', $volid);
>  
>              PVE::Storage::activate_volumes($storecfg, [$volid]);
>